Unable to Purchase Monthly Subscription on Preply Despite Multiple Attempts

I have been trying to buy a monthly subscription on the Preply app, but no matter what I do, the payment will not go through. My balance is sufficient, online shopping is enabled, and I have no restrictions on my cards. To be sure, I even tried with three different cards and three different browsers, but the issue persists.

This is extremely frustrating because I want to start lessons right away, yet the platform will not allow me to complete a simple subscription payment. There is also no clear explanation given for why the transactions keep failing.

I request urgent support from Preply to resolve this issue. The subscription system must work smoothly, and users should not have to waste time trying multiple methods to pay. Please fix this payment error so I can purchase my subscription without further problems.